Modern printing presses are capable of producing images on sheets at extremely high rates of up to more than one hundred pages per minute and even more. Instead of always reproducing the same page in a working cycle, as is the case with copying machines or offset litho presses, such machines successively produce complete sets of pages of a work, which are then frequently to be converted into a brochure, leaflet or booklet.
For processing stacks of sheets to make a brochure, leaflet or booklet finishing machines are certainly available. When it is desired to present the brochure, leaflet or booklet in a cover, such finishing machines comprise a gluing and encasing station in which a stack of sheets is firstly glued on a stack edge by passage past a rotating roll dipping into a liquid glue and the cover is then applied to the glue covered edge of the stack and folded around the same. Having regard to the irregularity of the sheets presenting themselves in a stack and in order to ensure that the edges of the finished product are neatly aligned, it is then necessary to trim the edges of the stack sheets in the cover. The resulting product therefore does not have the same dimensions as the sheets leaving the reproducing machine, as for instance DIN A 4. Moreover, the stacks of sheets are manually loaded on the finishing machine, something which depends not only on a previous alignment into stacks of sets of sheets emerging from the reproducing machine, but furthermore on human intervention for moving each assembled stack to the finishing machine. cl SUMMARY OF THE INVENTION
The finishing machine in accordance with the invention obviates all these drawbacks. In accordance with the invention such finishing machine comprises in succession: a takeover station for the sheets supplied by the reproducing machine; a device for the controlled retardation of the sheets received from the takeover station; a station for producing a horizontal stack of the retarded sheets; means for alignment of the stacked sheets; a gripping device for the stack of aligned sheets; a device for pivoting the gripped stack from a level position to a position on edge; and a device for gluing an edge of the stack and/or encasing of the stack in a cover. Using such combination of means, which may be of known design, it is possible to set up a continuous, completely automatic production line extending from the reproducing machine as far as a terminal station, which may be a collect station for the finished product. Taking into account the speed with which the sheets come off the reproducing machine, of for example 1 meter per second or more, it will be seen that the result is quite impressive. In effect, at such a speed of advance, the sheets will be conveyed in a practically random fashion unless same are subjected to a positive guiding effect. Thus in order to stack the sheets ejected in this manner, it is firstly necessary to retard same. In order to stack the sheets satisfactorily permitting correct alignment in the stack, the invention provides for controlled retardation of the sheets. The term "controlled retardation" employed herein means deceleration which is practically identical for each sheet from an initial speed down to a given reduced speed, making it possible for the sheets to be correctly superposed in a stack in such a manner that it is then sufficient to employ simple means to align the sheet in the stack. Since the invention then provides for the use of a stack gripping device for the aligned sheets, even during the pivoting of the stack out of a horizontal position into an on-edge position, the correct alignment of the sheet in the stack is maintained. Taken together such measures firstly render it possible to establish the correct alignment of the sheets in the stack as far as the encasing station, something rendering unnecessary any cutting operation in order to ensure alignment of the sheets in the final product.
In a preferred embodiment alignment of the sheets of the stack is not only provided for during the formation thereof but also after pivoting thereof into the on-edge position. In fact on transfer from the stacking station to the pivoting device for the stack, the alignment of the sheets may be lost to a certain extent. Furthermore when the stack of sheets is on edge, gravity may be utilized to improve accuracy of alignment. In either case alignment is preferably effected in two directions, that is to say in the direction of forward motion and in a direction perpendicular thereto.
In accordance with one significant aspect of the invention there is the provision of a retarding device for sheets received individually and in rapid succession with a view to stacking them, that is to say more particularly but not exclusively in a finishing machine of the type described hereinbefore. This device comprises at least one pair of rolls between which each sheet is engaged as from the reception thereof; one of the rolls is driven by a motor at a controlled speed and more particularly by a stepper motor controlled in such a manner that the speed of rotation of the rolls corresponds to the speed of supply of the sheets at the time of their engagement between the rolls and is reduced to a fraction of such speed at the moment at which the sheet is released by the rolls. Preferably the stepper motor rotates at a reduced speed while waiting for a sheet and is accelerated as soon as the arrival of a sheet is detected. In such a case a sheet detector is arranged on the input side of the rolls at a certain distance therefrom and is started when the leading edge of a sheet is detected by the detector, and the sheet retarding phase is started as soon as the passage of the trailing edge thereof is detected by the detector. Owing to this design the stepper motor is not operated in the wait mode and the control of the stepper motor is substantially facilitated because the retardation of the sheet is always started by the passage of the trailing edge thereof at the detector, such control therefore being independent of the length of the sheet.
In order to improve the accuracy of alignment of the cover in relation to the sheets in the stack the invention furthermore contemplates the provision of a precise metering of the quantity of glue utilized for each brochure, leaflet or booklet. Specifically the invention suggests an arrangement such that the encasing station comprises a rotating glue fountain roll dipping into liquid glue and a doctor selectively moved between a retracted position and an engagement position for engagement of the surface of the fountain roll in order to accumulate a mass of glue, which is presented to the edge of a stack when same moves on edge over the rotating fountain roll. The metering (rate of application) of the mass of glue is set by control of the doctor as function of the movement of the stack and the thickness thereof.
Other details and features of the invention will become apparent from the following description and the accompanying drawing.